This invention relates generally to the heating of liquids, and specifically to those devices wherein rotating elements are employed to generate heat in the liquid passing through them. Devices of this type can be usefully employed in applications requiring a hot water supply, for instance in the home, or by incorporation within a heating system adapted to heat air in a building residence. Furthermore, a cheap portable steam generation could be useful for domestic applications such as the removal of winter salt from the underside of vehicles, or the cleaning of fungal coated paving stones in place of the more erosive method by high-pressure water jet.
Joule, a wealthy Manchester brewer and English physicist who lived during the 19th century, was the first experimenter to show that heat could be produced through mechanical work by churning liquids such as water. Joule's ideas, as well as the work of others such as Lord Kelvin and Mayer of Germany, eventually led to the Principle of the Conservation of Energy. On the basis of this law, that energy can neither be created nor destroyed, numerous machines have been devised since Joule's early work. Of the various configurations that have been tried in the past, types employing rotors or other rotating members are known, one being the Perkins liquid heating apparatus disclosed in U.S. Pat. No. 4,424,797. Perkins employs a rotating cylindrical rotor inside a static housing and where fluid entering at one end of the housing navigates past the annular clearance existing between the rotor and the housing to exit the housing at the opposite end. The fluid is arranged to navigate this annular clearance between the static and non-static fluid boundary guiding surfaces, and Perkins relies principally on the shearing effect in the liquid, causing it to heat up.
A modern day successor to Perkins is shown in U.S. Pat. No. 5,188,090. Like Perkins, the James Griggs machine employs a rotating cylindrical rotor inside a static housing and where fluid entering at one end of the housing navigates past the annular clearance existing between the rotor and the housing to exit the housing at the opposite end. The device of Griggs has been demonstrated to be an effective apparatus for the heating of water and is unusual in that it employs a number of surface irregularities on the cylindrical surface of the rotor. Such surface irregularities on the rotor seem to produce an effect quite different than the forementioned fluid shearing in the Perkins machine, which Griggs calls hydrodynamically induced cavitation.
What is certain is that both Perkins and Griggs choose to employ a fixed gap clearance between the rotating rotor and the static housing. The choice thus made means that once the machine is assembled, the clearance cannot be changed. Although changing the clearance can obviously be achieved through subsequent machine disassembly and substitution of the rotor with one having either a smaller or larger diameter, such an act is both costly and time consuming to perform. Also once such a machine is installed in its intended application environment, it may turn out not to be best suited for the task at hand, and any subsequent rectification at the site of the application is best avoided if at all possible. An expensive option would to manufacture a series of machines, each exhibiting a slight variation in the clearance size. However, a better and more advantageous solution would be include the possibility for changing the clearance without having to disassembly the machine. This could also be easily done at the site of the application.
A further problem could occur in the event of any appreciable wear occurring during the design lifetime of the machine. Scale or other impurities that may on occasion pass through the clearance might cause sufficient damage to the surfaces that as a result, there is a noticeable drop in the efficiency of energy conversion. Were this to occur with such fixed clearance devices, the machine would require disassembly and repair. There would be an advantage however, if the damaged surfaces could be readjusted to reduce the operating clearance, thus saving the expense of performing a costly repair.
There therefore is a need for a new solution to overcome the above mentioned disadvantages, and in particular, there would be an advantage if the solution were simple to implement, resulting in an improved and easily controllable device, and especially whenever possible, without the need for the device to be torn down from the application in order to perform the required alterations/corrections in the event, for instance, a change in the desired operational characteristics of the device be sought for.